code: def get_macosx_target_ver():
      """Return the version of macOS for which we are building.
  
      The target version defaults to the version in sysconfig latched at time
      the Python interpreter was built, unless overridden by an environment
      variable. If neither source has a value, then None is returned"""
  
      syscfg_ver = get_macosx_target_ver_from_syscfg()
      env_ver = os.environ.get(MACOSX_VERSION_VAR)
  
      if env_ver:
          # Validate overridden version against sysconfig version, if have both.
          # Ensure that the deployment target of the build process is not less
          # than 10.3 if the interpreter was built for 10.3 or later.  This
          # ensures extension modules are built with correct compatibility
          # values, specifically LDSHARED which can use
          # '-undefined dynamic_lookup' which only works on >= 10.3.
          if (
              syscfg_ver
              and split_version(syscfg_ver) >= [10, 3]
              and split_version(env_ver) < [10, 3]
          ):
              my_msg = (
                  "$" + MACOSX_VERSION_VAR + " mismatch: "
                  'now "%s" but "%s" during configure; '
                  "must use 10.3 or later" % (env_ver, syscfg_ver)
              )
              raise DistutilsPlatformError(my_msg)
          return env_ver
      return syscfg_ver
  
imports: import importlib.util
  import os
  import re
  import string
  import subprocess
  import sys
  import sysconfig
  import functools
  from .errors import DistutilsPlatformError, DistutilsByteCompileError
  from ._modified import newer
  from .spawn import spawn
  from ._log import log
label_desc: Use image node_id 5 for calling a global function with example usage: get_macosx_target_ver() and returns: syscfg_ver, env_ver